Performance of Three-phase Inverter Using Multiple Bidirectional Choppers for 1.5-kV PV Systems Capable of Wide MPPT Range

Abstract

This article proposes a new three-phase in-verter for utility-scale photovoltaic (PV) systems where multiple cascaded bidirectional choppers and a three-phase transformer with a three-legged core are used. The inverter is characterized in that a wider range of dc input voltages is available without using a boost converter. Consequently, a wide MPPT range can be achieved. Furthermore, there is no high-frequency harmonic current flowing in the stray capacitance of the PV array because the negative terminal of the PV array and the ground are directly connected. Thus, the parallel operation of the inverters becomes easier compared with the conventional 2- or 3-level PWM inverters. The operating principles and control method of the inverter along with the loss analysis are presented in this article. The validity of the inverter is proved by conducting experiments using a 1.5-kW downscaled model.